Jay Griffiths is a five-star, card-carrying member of the hellfire club. In just a few pages of her strange, utterly compelling travel book, this rebel deluxe tells us of her opposition to mining, logging and missionaries (especially the American rightwing evangelist sort). She also savages golf, factory farming and out-of-town shopping centres, and adds to the tally of complaints with tirades against cartography, walls, corridors, timekeeping, television, capitalism and Christianity.

At times she seems at odds with the whole of western civilisation, because she sees it as hostile to the thing she cherishes most dearly. According to the author, wilderness - as both physical landscape and state of mind - has been under siege for thousands of years from culture. In our antagonism to nature, Griffiths feels she has found the root causes of our social discontents. Yet her journey is also autobiographical, as she diagnoses a lack of contact with wilderness as the source of her own spiritual crisis.

To cure herself, and to examine the ills of the west, Griffiths spent seven years on her version of the Lawrentian savage pilgrimage, to meet those she saw as the keepers of the sacred flame - tribal peoples who live in deep intimacy with their respective landscapes. Each destination was symbolised by one of five "elements": the Amazonian forest of South America (earth), Arctic Canada (ice), Bajo, a small island off Sulawesi (water), the Australian outback (fire) and the montane forests of West Papua (air).

As simple adventurer, Griffiths is cut from the same stone as people like Dervla Murphy and Christina Dodwell. She goes solo into remote places and takes on gruelling challenges. In the South American rainforest, for example, she explores ayahuasca, a potent hallucinogenic plant that soon has her in a deeply vulnerable trance surrounded by singing shamans, hair clotted with her own vomit and mind swimming with visions of herself as jaguar wandering the streets of Oxford. Rather than being deterred by such experience, Griffiths embraces it, seeing the drug as a first portal to the meaning and virtue of wildness.

Her principal sources, however, are not chemicals, but indigenous people. Griffiths gets on first-name terms with a huge array of indigenes from four continents. Part of her achievement is to gain acceptance and intimacy in ways that a lone male traveller might find difficult. Griffiths is herself often vulnerable, although she is not above using sexual wiles to win acceptance or get her way. But the key quality she displays as a traveller is a capacity simply to be absorbed and to listen.

Her text is shaped by the words of her many contacts, as she tries to unravel the meaning of landscape and wilderness to those that actually live there. It is this intellectual journey, rather than a mere travelogue, that is the substance of her book and distinguishes her from - and places her a cut above - writers such as Murphy and Dodwell.

The set-piece essays, while often covering the same ground more than once, set up connections and resonances between each other that help illuminate her underlying thesis. From its origins on the Mediterranean shore, European civilisation has operated on a binary philosophy which pitches culture in fundamental opposition to wilderness. This has led western imperialists into ruthless mistreatment of peoples and their wilderness lands around the world, and lies behind a bogus historiography that has been used to justify policies of genocide and displacement.

Griffiths is especially good at unearthing the way the very structures of our language have set us against "wild" people and places. She is equally skilled in showing how the languages of native peoples observed a reverse set of values. She argues that one of the first tasks of her much-hated missionaries was to rob tribal communities of their own language. The extirpation of culture then went hand in glove with the theft of land itself. Missionaries and illegal mining on tribal lands are therefore two parts of the same invasive programme.

One failing of Griffiths's polemical style is its simplification of some of the arguments. The wilderness is, for her, always in a distant setting, such as the Amazon or the Australian outback. She has nothing to say on wilderness at home, nor on more positive European responses to the wild. To give one example, the blackbird I can hear singing now in my garden as I write is a point of contact between the cultural and the wild. Our gardens are a form of open woodland, often far richer in wildlife than the surrounding farmland. Blackbirds thrive better in gardens than in any other habitat. The reason Amerindians don't fear and destroy the forest is that they have domesticated it by their knowledge and their cultural appropriation of its qualities. In short, rainforest is for them a form of garden. The late Colin Tubbs, the distinguished ecologist of southern England, estimated that the region's biodiversity was greatest, not when a neolithic axe first echoed in the wildwood 5,000 years ago, as Griffiths would probably have us think, but at the end of the 18th century. Culture and nature have been in close symbiosis even in Britain, and while we may now have lost that balance, environmentalism is one of the largest social movements of our age. Feather-crowned Amerindians may be icons of that process, but the notion that wilderness is central to the wholesome society has its own indigenous roots in Europe.

Griffiths's style of writing in Wild presents a completely separate kind of challenge. Her prose necessitates a breathless high-altitude trek from peaks of great lucidity to troughs of repetition and hackneyed phrase, often in quick succession. A key problem is her penchant for wordplay - puns, alliteration, paradox, figures of speech - which she strings together in long, associative chains, often for their own sake and without regard for meaning or the fact that she has said the same thing elsewhere.

One wonders why her editor didn't attempt to curb the excess or excise the duplication. Presumably he or she concluded that the faults were a part of Griffiths's method, a natural by-product of her creative exuberance. Yet when the author herself restrains these tendencies, her blend of poetic insight and observational detail results in writing of luminous power. Here is Griffiths on the conflicting emotions provoked by her first Inuit whaling expedition: "It was shot once then twice more. A minute before, spray was jetting from its blowhole. Three cracks of rifle fire, and now blood fountained into the air; plumes of blood in the water blooming, hot and flourishing. The beluga was hauled on to the shore, its smooth white body bleeding; the violent perfection of blood on snow. And its smile curled shy like a child's while the whale head snuggled down onto the shore ice, its dark grey eyes wise to death."

For all its occasional ill-discipline, Wild is easily the best, most rewarding travel book that I have read in the last decade. It is a bold rag-bag of a work, full of pagan energy, and at times richly beautiful. The author keeps the reader engaged with her challenging insights and ideas. In Griffiths, wilderness has found an eloquent new champion who is full of exceptional promise.